#include <stdio.h>

int main()
{
    //FILE* fp = fopen("log.txt", "w");
    FILE* fp = fopen("log.txt", "a");
    if (fp == NULL)
    {
        perror("fopen");
        return 1;
    }
    fprintf(fp, "hello world,%d,%s,%lf\n", 10, "lj", 3.14);

    fclose(fp);

    return 0;
}
